Method for reducing the pilling tendencies of fabrics



r H amass Pa tented Feb.17,1959

METHOD FOR REDUCING THE PILLING TENDEN'CIES OF FABRICS Dmitry M.Gagarine and Henry Repokis, Clemson, S. C., assignors to DeeringMilliken Research Corporation, Pendleton, S. C., a corporation ofDelaware No Drawing. Application March 12, 1954 Serial No. 415,966

18 Claims. (Cl. 117-103) This invention relates to fabrics resistant topilling and more particularly to pill resistant fabrics containingapproximately 40% or more non-cellulosic, synthetic, organic fibers,herein referred to for convenience simply as synthetic fabrics, and tomethods for reducing the pilling tendencies of fabrics containing 40% ormore non-cellulosic, synthetic, organic fibers.

The phenomenon of pilling has been encountered for years with woolenfabrics when such fabrics are worn as clothing and is apparently causedby lint from the textile material becoming entangled with the surfacefibers and forming small pills or balls. With woolen fabrics, however,pilling has presented no serious problem since the pills are veryloosely held and either fall off or are unconsciously brushed off beforethere is a serious accumulation.

With the advent of non-cellulosic synthetic fibers, and particularlypolyester fibers, it was found that fabrics composed to a large extentor entirely of such fibers not only pill as do woolens but that thepills on such ,materials cling tenaciously, cannot be brushed off, and

can only be pulled off with effort. Because of this, the pills soonreach such an accumulation on such materials, and in particular onpolyester materials, as to result in an unsightly appearance andembarrassment to the wearer of clothing made therefrom. It can be seen,therefore, that a method to impart resistance to pilling in syntheticfabrics would be a welcome advance in the art.

According to this invention non-pilling characteristics are imparted tosynthetic fabrics by applying to the fabric an aqueous emulsion of avinyl resin having a softening point below about 350 F., drying thefabric and heating the same at least momentarily to a temperature atleast as high as the softening point of the resin.

Vinyl type resins have in the past been employed in a few instances toobtain shrinkage control in woolen fabrics although their use for thispurpose never became widespread for the reason that it was found thatcertain thermosetting resins were far superior for this purpose. Vinyltype resins have also been employed on cotton textiles to increase thebody and for other purposes. It will be apparent that such uses of thevinyl resins are completely non-analogous to their use in the presentinvention where no severe shrinkage problem exists and any increase inthe body of the material is purely incidental.

The method by which the vinyl resin treatment of this inventiondecreases the tendency of synthetic fabrics to pill is not fullyunderstood. Pilling difliculties in synthetic fabrics are generallyassumed to be due, at least in part, to the high strength of thesynthetic fibers and the great force necessary to dislodge the fibersfrom the surface of the material but the resin treatment of thisinvention would not be expected to lower the tensile strength of thepolyester fibers and would tend to make the surface fibers even moreditficult to dislodge. In fact, many experiments conducted in connectionwith this invention to establish the reason or reasons that a givenfabric does or does not pill have failed to give a. completelysatisfactory answer and appear to contradict previously accepted ideasin some respects so that a satisfactory theoretical explanation of thenew process of this invention at this time cannot be given.

It is an advantage of the present invention that the process ofrendering synthetic fabrics non-pilling is exceedingly simple and doesnot require equipment not readily available in most textile finishingplants. It is a further advantage of the invention that it makespossible the production of non-pilling synthetic fabrics in aninexpensive manner. However, the most important advantage of theinvention is that the treated fabrics are, under optimum condition,substantially unchanged in hand from the untreated materials. Syntheticfabrics are exceedingly sensitive to surface treatments and manyprocesses that are routinely employed on woolen fabrics for variouspurposes cannot be employed Without rendering the hand of the syntheticmaterial unacceptable. For example it has been found to be impracticalto apply to polyester fabrics certain thermosetting resins of typescommonly applied to woolens because their application to polyesterfabrics completely ruins the hand of the material.

Substantially any vinyl type resin can be employed in the preparation ofnon-pilling fabrics according to this invention as long as the resinpossesses the necessary physical properties of being water emulsifiable,and of having a softening point below about 350 F. Illustrative examplesof suitable resins are polymers or copolymers of compounds asillustrated by vinyl chloride, vinyl acetate or other vinyl esters,styrene, methyl acrylate, methyl methacrylate or others esters ofacrylic or methacrylic acid, butadiene, and isoprene. If desired, thevinyl resin may also contain a plasticizing agent.

Vinyl resins of the above types vary Widely in their film formingcharacteristics depending upon the amount and type of plasticizeremployed, the degree of polymerization and other factors. Variousaqueous emulsions of resins of the above types may form on drying andheating a readily pliable film, a tough stiff film, a very brittle filmor only a broken granular mass. If an aqueous emulsion of a resin formsa granular mass on drying and heating, it is considered in thisspecification as being devoid of film forming characteristics and it isindeed surprising that such resins give results, in some instances,superior to resins having film forming propertics.

The vinyl resin should be applied to the fabric in amounts of at leastabout 0.4% by weight since smaller quantities sometimes do not result inthe treated fabric having the desired degree of anti-pilling propertiesand amounts of at least 0.8% by weight of the fabric are generallypreferred. If the resin has appreciable film forming ability and isapplied in amounts greater than about 5%, the hand of the treatedpolyester fabric is sometimes adversely affected. Resins substantiallydevoid of film forming characteristics can, in most instances, be safelyapplied in amounts up to 10% or more. However, it is generally notadvantageous for economic reasons to apply more than about 4% of thevinyl resin so that the preferred range is from about .8 to 4% by weightof the fabric.

Vinyl resins suitable for use in this invention are, in many instances,commercially available as aqueous emulsions and substantially all ofthese preparations may suitably be employed in the new process whendiluted to an appropriate concentration. If an aqueous emulsion of aselected vinyl resin is not commercially available, one can readily beprepared by dispersing the powdered dry resin in an aqueous solvent witha suitable emulsifier or by emulsion polymerization of a selectedmonomer or combination of monomers. When preparing an emulsion from thepowdered polymer or from the monomer, substantially any emulsifier,non-ionic, cationic, or anionic that is capable of resulting in asatisfactory emulsion of the resin in an aqueous solvent may beemployed. The preferred emulsifying agents are ammonium salts of fattyacids or other materials of this type that are destroyed by the dryingoperation and cannot thereafter act as rewetting agents.

When an emulsion of a vinyl resin substantially devoid of film formingcharacteristics is employed, the hand of the resulting fabrics isfrequently quite satisfactory without any special measures being taken.However, if one is employing a film forming emulsion, it has been foundthat a better hand is often obtained if the emulsion is applied incombination with a textile softening agent and even when employingnon-film forming emulsions, the hand can sometimes be improved by thisprocedure. It has been found, however, that the use of a softening agentfrequently requires the use of larger quantities of resin for equivalentresults.

Any of the many commercially available textile softening agents can beemployed for hand improvement. These agents are generally surface activetype compounds with insufiicient solubilizing groups to give highdetergency and one can employ anionic, cationic or non-ionic materialswith satisfactory results. Illustrative examples of anionic softeningagents are salts of fatty carboxylic, carbamic or sulfonic acids such asthose sold under the trade names of Avitone A by E. I. du Font, andAhcovel E by Arnold Hoffman & Co. Examples of suitable non-ionicsoftening agents are polyglycol ethers, esters, or amides such as thosesold under the trade-names of Ethofat 60/15 and Ethomid HT 25 by Armourand Co. and under the name Avcosol 100 by American Viscose. And examplesof suitable cationic softening agents are amines and quaternary ammoniumcompounds such as those sold under the trade names of Ahcovel G byArnold Hoffman & Co., Lupomin Q by Jacques Wolf and Co., Onyxsan HSB byOnyx Oil and Chemical, Triton K60 by Rohm & Haas and Armac HT, Ethomeen18/15 and Texsoft Cone. by Armour and Co. As a general rule the cationicmaterials are preferred as they lend themselves well to application withthe vinyl resins and since in addition to resulting in a better hand,they also decrease the tendency of the treated fabrics to gather staticelectricity.

The softening agent can be applied concurrently with the resin or it maybe applied before or after resin application. A slightly better hand isoften obtained if the resin is first applied and the softening agent isthen applied immediately thereafter although it is sometimes moreconvenient to apply the softening agent to the fabric immediatelyproceeding the resin application. The softening agent should be appliedin amounts equal to at least about 0.1% :by weight of the fabric andbest results are obtained if the softening agent is applied in amountsequal to from about 0.5% to 2% by weight of fabric. No added benefitsare generally obtained by applying more than about 4% by weight of thesoftening agent and because of economic factors, such large quantitiesare not usually employed to advantage.

A convenient and generally satisfactory procedure for applying theemulsion to a polyester fabric comprises simply immersing the fabric inthe emulsion, for instance, in a pad :box, and then removing excessliquid, for example by passing the fabric through a pair of pressurerollers. The weight gain resulting from such a procedure is generallyfrom about 50 to 100% of the dry weight of the textile materialdepending upon the type of fabric and the pressure on the squeeze rolls.In this method of application, the amount of vinyl resin deposited onthe fabric depends primarily upon the amount of liquid remaining in thefabric after passage through the squeeze rolls and upon theconcentration of resin in the emulsion. Since, as has been previouslystated, the weight of resin deposited on the fabric should be equal tofrom about 0.4% to 10% and preferably from about 0.8% to 4% of the dryweight of the fabric, it can :be seen that the concentration of vinylresin in the emulsion when employing this method of application shouldbe from about 1% to 12% and preferably from about 2% to 8% by weight ofthe emulsion.

A novel and preferred procedure for applying the vinyl resin which givesa better hand and more desirable pilling characteristics comprisesrepeatedly passing the fabric into the emulsion and gradually adding amaterial to break the emulsion so that the resin is deposited on thefabric as the emulsion is broken. The emulsion can be convenientlybroken by any suitable procedure, such as for instance adding a materialto destroy the effectiveness of the emulsifying agent. For example, if awater soluble salt of a fatty acid is employed as an emulsifying agent,the emulsion can be broken by adding a salt of a polyvalent metal whichreacts with the emulsifying agent to form a water insoluble material.Since in this procedure for applying the vinyl resin substantially allof the resin is eventually deposited on the textile material, theprimary consideration is the ratio of total weight of resin to weight offabric and the exact concentration of the emulsion is of littleimportance.

Applying the vinyl resin by the exhaustion technique described above notonly results in a better hand and better pilling characteristics in mostinstances but is also advantageous in instances where padding equipmentis not available since the procedure can be conveniently performed in adolly washer or dye beck. Most apparatus of this type 'is designed tobest operate with the weight of liquid equal to from about 5 to timesthe weight of the fabric, and, therefore, the concentration of vinylresin in the emulsion at the beginning of operations should generally befrom about .008 to 0.8% by weight of the emulsion. there being depositedon the textile material an amount of vinyl resin equal to from about .8to 4% by weight of the textile material which is within the preferredrange.

It is an advantage that the exhaustion technique of resin applicationcan readily be combined with a softener application so that both can beapplied to the fabric in a single bath. One suitable procedure foraccomplishing this result is to employ a cationic softening agent suchas a fatty amine that is only soluble in acid solution. The fabric to betreated is then loaded into a dye beck with an acidic solutioncontaining the desired quantity of the softening agent and a molarquantity, equal to at least that of the emulsifying agent in theemulsion to be subsequently added, of a metal salt, such as zincchloride or other inorganic salts of zinc or metals such as calcium,magnesium and lead, capable of reacting with the emulsifying agent togive a water insoluble material. The pH is then gradually raised toresult in the deposition of the softening agent on the fabirc. When thepH has reached a basic value, a concentrated dispersion of the resinemploying an anionic dispersing agent, such as a sodiumalkylarylsulfonate, sodium oleate or other water soluble salt of anorganic acid, is then added to the bath and the pH lowered verygradually. The dispersing agent reacts with the inorganic salt so thatthe emulsion is broken and deposits completely on the fabric before thepH becomes more acidic than about pH 6. Other satisfactory techniquesare also available and will suggest themselves to those skilled in theart in view of the above.

The temperature of application by either of the above procedures is notcritical and the resin can be applied at any convenient temperature fromabout the solidification temperature of the emulsion to the boilingtemperature of the aqueous solvent. Excellent results are ob.

As can be seen, this concentration results in tainable at roomtemperature which is preferred for convenience.

Drying of the fabric after treatment can be effected at any convenienttemperature at which the fabric is not damaged. As is Well known tothose skilled in the art, however, some synthetic fibers, such aspolyester materials, should not be heated for prolonged periods attemperatures of above 200 or 250 P. so that a drying temperature belowthis range is generally advantageous. On the other hand, it is generallyadvantageous to dry the fabric at a temperature in excess of thesoftening temperature of the vinyl resin employed if this is possiblewithout injury to the material. In instances where the softeningtemperature of the vinyl resin is above about 250 F., the fabric can bedried at a lower temperature and at or near the completion of drying,heated to a temperature above the softening point of the resin for onlya sufficient period of time to actually obtain a softening of the resin.Since this requires only a few seconds, it can be readily accomplishedwithoutmaterial damage to the fabric if the melting point of the resinis below about 350 F.

The invention will now be illustrated by the following specific examplesin which all parts are by weight unless otherwise specified:

Example I ,An emulsion containing 2.6% solids is prepared by mixing 30parts of a commercially available aqueous emulsion containing 45% of apolyvinyl chloride resin (Polyco 446) with 500 parts of water. Thisemulsion when dried and heated in an open dish forms only a granularmass. A sample of a polyester textile material containing 55% polyesterfibers and 45% wool fibers is then immersed in the emulsion untilthoroughly wetted and then passed through squeeze rollers to give aliquid pick-up of approximately 84% based on the dry weight of thetextile material. The sample is then dried and cured for 10 minutes at200 F.

The pilling characteristics of the treated samples are then compared tothose of an untreated sample .by placing both in a pilling machine inwhich the samples in each instance are first brushed with stiff nylonbristles for minutes to work up the nap and then rubbed againstthemselves for 3 minutes. The number of pills on the treated sample arethen visually compared to the number on the. untreated sample. Theuntreated sample is in each instance rated at a value of 100 and thetreated sample is rated from 0 to 100 dependingupon the number of pillsas compared to the untreated sample. If for instance the untreatedsample has a total of 50 pills per unit area and the treated sample hadone pill per unit area, the untreated sample would be given a rating of100 and the treated sample would have a rating of 2.

In this instance the treated sample containing approximately 2.2%polyvinylchloride polymer had a rating of 0 as compared to the untreatedfabric. The treated sample'was then subjected to 3 Varsol tumblejar drycleanings of 20 minutes each and again tested for its pillingcharacteristics. The sample againhad a rating of 0. In other words, thesample of material resulting from this example was completely resistantto pilling both before and after 3 dry cleanings.

The hand of the treated sample, which as previously explained, is animportant consideration when dealing with polyester fabrics, was quiteacceptable although somewhat raspy.

Example 11 An emulsion is prepared containing 1.65% solids by adding 15parts of a commercially available polyvinyl acetate emulsion, havingsubstantially no film forming characteristics (Polyco 117 SS), to 500parts of water. In the resulting solution there are treated two samplesof polyester materials, the first being composed 100% made,

of polyester fibers (Dacron) and the second containing 55 polyesterfibers and 45% wool fibers. In each instance the treated samples arepassed through squeeze rolls to give a liquid weight gain ofapproximatey based on the dry weight of material and the samples arethen dried and cured 10 minutes at 200 F.

When samples above were tested for pilling characteristics as describedin Example I, the sample composed entirely of polyester fibers gave avalue of 15 before and 25 following three 20 minute dry cleanings. Thehand of the sample was good although slightly boardy. The second samplecomposed of 55% polyester fibers and 45% wool fibers had a pillingrating of 10 before dry cleaning and a rating of 20 after three 20minute Varsol washes. The hand of the wool-polyester fabric wasexcellent and only very slightly difiercnt from the hand of theuntreated material.

Example 111 An emulsion is prepared containing 2.4% solids by diluting30 parts by Weight of a commercially available aqueous acrylic emulsioncontaining 40% solids (Polyco 319) with 500 parts of water. A sample ofa polyester fabric, plain weave, which had been previously dyed is thenpadded through the emulsion and passed through squeeze rolls to give aliquid pick-up of approximately 80%. The material is then dried on arenter frame, sheared in the usual manner and its tendency to pilltested by the procedure of Example I. The pilling characteristics of thetreated material are greatly improved as compared to the untreatedcontrol and are found to improve still further following three Varsoldry cleanings. The hand of the treated fabric is excellent and canhardly be distinguished from that of the untreated control. p 7

Example IV In each of three suitable containers there is placed 500parts by Weight of water and to the first there is added 10 parts byweight of a commercially available acrylic resin emulsion containing 40%by Weight of s lids (RhopleX WG-9), to the second there is added 20parts by weight of-the acrylic emulsion and to the third there is added30 parts by weight of the acrylic emulsion. Separate samples of amaterial composed of 55% polyester fibers (Dacron) and 45% wool fibersare then padded through each of the three emulsions to give in eachinstance a liquid pick-up of approximately 80%. This results in therebeing deposited on the three samples 0.6 5%, 1.3%, and 1.9% respectivelyof acrylic resin. The three samples are then dried and tested against acontrol sample for pilling, hand and mark-off. The sample of material onwhich there is deposited 0.65% resin shows only a slight pillingtendency, has an excellent hand and gives no mark-off. The sample onwhich there is deposited 1.3% by weight of resin displays only a veryslight tendency to pill, has a good hand and no mark-off. The sample onwhich there is deposited 1.9% resin displays no pilling whatsoeveralthough the hand is slightly firm and the material has a slightmarkoif. The hand of the last two samples is noticeably improved bytopping the material with /2% of a commercial nonionic softening agent(Ethofat C15).

Example V of ammonium hydroxide (28% NH Stirring produces a goodemulsion.

In a small dyebeck there is placed 5,000 parts by weight of water andthe beck loaded with 100 parts by weight of a fabric composed of 55%polyester fibers (Dacron) and 45% wool fibers. The above describedemulsion is then added to the beck and the temperature gradually raisedto 200 F. in about 1 hour. The exhaustion of the resin onto the fabricis substantially complete. The fabric is then dried and tested for itsphysical properties. It is found to have a good hand and forms no pillswhen tested by the procedure described in Example 1.

Example VI To 5,000 parts by weight of water there is added 60 parts byweight of a commercially available aqueous emulsion of abutadiene-isoprene copolymer containing 32.5% solids (Hycar 1500 x 151).A sample of material woven from 55 polyester fibers (Dacron) and 45%wool is then padded through the emulsion and passed through squeezerolls to give a liquid pick-up of approximately 85%. The material isthen dried and found to have a good hand and to be substantially free ofpilling tendencies.

Example VII In a suitable container there is placed 100 parts by weightof a wool-polyester fabric, containing 55 polyester fibers (Dacron) and45 wool, and 3,000 parts by weight of cold water. The cloth is agitatedgently while there is added a mixture containing 0.5 part by weight ofsoybean fatty amines (Armeen SD), 0.5 part by Weight of zinc chloride,and 1 part by weight of acetic acid. The cloth is then agitated anadditional 20 minutes at room temperature at the end of which time thereis slowly added suflicient ammonium hydroxide to raise the pH to a valueof 7.5. To the slightly basic solution there is added 6 parts by weightof a commercially available aqueous acrylic resin emulsion containing40% by weight of solids (Rhoplex WB-9), with continuous agitation. Thereis then added very slowly sufiicient sulfuric acid to lower the pH to avalue of 6.8 which results in a uniform exhaustion of the resin onto thecloth. The cloth is then passed through squeeze rolls and dried. Thedried material has an excellent hand and pilling tendencies are reducedto within satisfactory limits.

Example VIII Example IX Example VII is repeated except that in place ofthe acrylic resin there is substituted 12 parts by weight of acommercially available aqueous polystyrene resin emulsion containing 50%solids (Monsanto Polystyrene 601- 40). The exhaustion of the resin ontothe fabric again proceeds in a satisfactory manner and the treatedmaterial has a good hand and satisfactory pilling characteristics.

Example X Example VII is repeated except there is substituted for thewool-polyester fabric an equal weight of a wool-polyacrylonitrile fabriccontaining 55% polyacrylic fibers (Orlon) and 45 wool. The hand of thetreated material is excellent and the pilling tendencies of the woolpolyacrylic fabric are measurably reduced.

Example XI Example VII is repeated except that in place of thewool-polyester fabric there is substituted an equal weight of awool-nylon fabric containing wool and 45% nylon. Again the hand of thetreated material is excellent and the pilling tendencies of thewool-nylon fabric are measurably reduced.

Having thus described our invention What we claim is:

1. A method for reducing the pilling tendencies of fabrics containing atleast about 40% staple length polyester fibers which method comprisesapplying to the fabric an aqueous emulsion of a thermoplastic vinylresin having a softening point above about 250 F. but below about 350F., and thereafter heating the fabric at least momentarily to atemperature at least as high as the softening point of the resin.

2. The method of claim 1 wherein the resin is an acrylic resin.

3. The method of claim 1 wherein the resin is a polystyrene resin.

4. The method of claim 1 wherein the resin is a butadiene-isoprenecopolymer.

5. The method of claim 1 wherein the resin is a vinylchloride polymerresin.

6. A method for reducing the pilling tendencies of fabrics containing atleast 40% staple length polyester fibers which method comprises applyingto the fabric from about 0.4% to 10% by weight of a thermoplastic vinylresin having a softening point above about 250 F. but

- below about 350 F., and from about 0.1% to 4% of a textile softeningagent and thereafter heating the fabric to a temperature at least ashigh as the softening point of the resin.

7. A method for reducing the pilling tendencies of fabrics containing atleast 40% staple length polyester fibers which method comprises paddingthe fabric through an aqueous emulsion of a thermoplastic vinyl resinhaving a softening point above about 250 F. but below about 350 F. toresult in there being deposited on the fabric from about 0.4% to 10% byweight of the resin, drying the fabric and thereafter heating the fabricat least momentarily to a temperature at least as high as the softeningpoint of the resin.

8. A method according to claim 7 wherein the resin emulsion issubstantially devoid of film forming characteristics.

9. A method according to claim 7 wherein the resin is an acrylic resin.

10. A method according to claim 7 wherein the resin is a butadieneresin.

11. A method for reducing the pilling tendencies of fabrics containingat least 40% staple length polyester fibers which method comprisesimmersing the fabric in an aqueous emulsion of a thermoplastic vinylresin containing from about 0.4% to 10% resin based on the weight of thefabric, breaking the emulsion to result in said resin being exhaustedonto said fabric, drying the fabric and thereafter heating the fabric toa temperature at least as high as the softening point of the resin, saidresin having a softening point above about 250 F. but below about 350 F.

12. A method for reducing the pilling tendencies of fabrics containingat least 40% staple length polyester fibers which method comprisesimmersing the fabric in an acidic aqueous medium containing from about0.1% to 4%, based on the Weight of fabric, of a cationic textilesoftening agent and an inorganic heavy metal salt, gradually raising thepH of the solution until the medium is slightly basic, adding an aqueousemulsion containing from about 0.4% to 10%, based on the weight offabric, of a thermoplastic vinyl resin having a softening point aboveabout 250 F. but below about 350 F., said emulsion being formed with ananionic emulsifying agent, gradually lowering the pH to an acidic valueto result in the exhaustion of the resin onto the fabric, and drying andheating the fabric to a temperature at least as high as the softeningpoint of the resin.

13. The method of claim 12 wherein the cationic softening agent is afatty amine and the heavy metal salt is zinc chloride.

14. The method of claim 13 wherein the resin is an acrylic resin.

15. The method of claim 13 polystyrene resin.

16. The method of claim 13 wherein the resin is a butadiene resin.

wherein the resin is a 17. The method of claim 12 wherein saidemulsifying agent is decomposed by said heating.

18. The method of claim 17 wherein said emulsifying agent is a fattyacid ammonium salt.

References Cited in the file of this patent UNITED STATES PATENTS RossinSept. 8, 1953

1. A METHOD FOR REDUCING THE PILLING TENDCIES OF FABRICS CONTAINING ATLEAST ABOUT 40% STAPLE LENGTH POLYESTER FIBERS WHICH METHOD COMPRISESAPPLYING TO THE FIBRIC AN AQUEOUS EMULSION OF A THERMOPLASTIC VINYLRESIN HAVING A SOFTENING POINT ABOVE ABOUT 250*F. BUT BELOW ABOUT350*F., AND THEREAFTER HEATING THE FABRIC AT LEAST MEMENTARILY TO ATEMPERATURE AT LEAST AS HIGH AS THE SOFTENING POINT TO THE RESIN.